Construction of radioactive lightning arresters

ABSTRACT

A radioactive, ionizing lightning arrester, or conductor is provided with at least one brush attached to an anemometer type mechanism in such a way that the radioactive source of the arrester will be automatically cleaned as the wind blows. The arrester is provided with a discontinuous meteal surface which is spaced apart from and surrounds the radioactive source, and which is further electrically insulated from the remainder of the device so that it acts as an accelerating anode.

United States Patent [191 Fornes Puget [4 1 July 22,1975

CONSTRUCTION OF RADIOACTIVE LIGHTNING ARRESTERS Enrique Fornes Puget, Madrid, Spain Assignee: Nuclear Iberica S.A., Madrid, Spain Filed: Aug. 7, 1972 Appl. No.: 278,446

Inventor:

Foreign Application Priority Data Aug. 7, 1971 Spain 394004 US. Cl 317/61; 15/21 R; 15/246;

174/4 C; 317/262 AE Int. Cl. H02h 9/04 Field of Search 317/61, '262 AB, 2 F;

174/3 R, 4 R, 4 C; 15/21 R, 246

References Cited UNlTED STATES PATENTS 3/1878 Johnson et a1. 174/211 UX 1,778,891 10/1930 Earnhardt 317/61 2,128,408 8/1938 Greiner 3,662,083 5/1972 Constant 317/61 X Primary Examiner-James D. Trammell Attorney, Agent, or Firm-Fleit & Jacobson [5 7] ABSTRACT A radioactive, ionizing lightning arrester, or conductor is provided with at least one brush attached to an anemometer type mechanism in such a way that the radioactive source of the arrester 111 be automatically cleaned as the wind blows. The arrester is provided with a discontinuous meteal surface which is spaced apart from and surrounds the radioactive source, and which is further electrically insulated from the remainder of the device so that it acts as an accelerating anode.

5 Claims, 5 Drawing Figures PATENTEDJUL 22 I915 FIG.5

FIGA

CONSTRUCTION OF RADIOACTIVE LIGHTNING ARRESTERS This invention relates to improvements in the construction of radioactive, ionizing lightning arresters, or conductors and more particularly to improvements in lightning arresters of the type which comprise a radioactive source emitting alpha particles in one or more nuclei disposed on the outer surface of a support in the form of a body of revolution which is mounted concentrically about a metal bar or rod which is connected to earth.

At present lightning arresters of the type indicated are known, with which it is attempted to obtain a better radius of action than with conventional lightning arresters; however in practice the efficiency of said lightning arresters is limited by the capacity of ionization of the air in a permanent and effective manner.

This invention has the object of obtaining a greater ionization power both economically and safely, as well as the ability of ensuring said high capacity of ionization along with a very long useful life of the lightning arrester. This object is achieved simultaneously and conjointly by the three following measures:

1. Increasing the diffusion of the ions produced by the alpha particles emitted by the radioactive source and also increasing the acceleration of said ions, and therefore their capacity of producing secondary ionization by collision with other molecules of the air.

2. Maintaining the surface of the radioactive source clean from deposits of dust, smoke, etc., which would absorb either completely or partially the emission of alpha particles, thus nullifying or reducing the ionization capacity of same.

3. Using alpha-particle-emitting sources which, being sealed as necessitated by the safety measures required for its use, process a high power of ionization for the exterior emission of alpha particles in sufficient quantity and with the greatest possible energy.

In order to achieve the first aim indicated, there is used a device intended to accelerate the primary ions produced by the collision of the alpha particles with the air particles. This device consists of a discontinuous metal surface, like a grid or grating, concentrically situated around the sourceholder support at a suitable distance therefrom in accordance with the maximum travel of the alpha particles in the air. The metal surface is electrically insulated from the rod connected to earth by means of several supports made of suitable insulating material, and accordingly there is created a potential at the metal surface in respect to the earth, which potential is particularly high in the presence of a storm cloud, thus acting as an accelerating anode of the ions produced. The accelerating anode thereby produced first prevents the recombination of the ions of different signs in the vicinity of the ionization zone, thus increasing the action of the actual electrostatic field existing between the cloud and the earth. Second the accelerating anode increases the production of secondary ions by collision of the primary ions with other molecules in the air.

As a result of these two phenomena there is achieved an increase in the quantity of ions produced and also an increase in the speed of the ions as they travel. Moreover, dispersing action of the air is also eliminated. However, the main feature of this invention is that the great majority of the acceleratedions pass through the accelerator anode, which is due to its grating-like form, that is its discontinuous surface, in the same way in which electrons pass through the grid of a thermionic valve. Otherwise the ions would cause the formation of an ion cluster around said anode, in accordance with a known phenomenon, thus nullifying potential difference present and therefore the effect previously described.

In order to achieve the second aim mentioned there is provided a mechanism for continual self-cleaning of the source, the mechanism being mounted on the lightning arrester. This mechanism utilizes the action of the wind against a number of cups arranged at the end of a number of arms joined to the outer body of a special, self-lubricated high-durability bearing, whose inner body is mounted onthe rod of the lightning arrester. Hanging from the rotating unit is an arm provided at its free end with a wiper or brush made from a soft and durable material, the wiper or brush adapted to slide smoothly over the radioactive source. The other end of the arm, that is the end not carrying the wiper or brush, rocks on a pivot in such a way that the action of the centrifugal force of rotation causes it to lift when the force of the wind exceeds a certain perdetermined value. As a result, the brush operates for sufficient time necessary to keep the source clean and avoids wear on the source.

In conventional ionizing lightning arresters the radioactive source is exposed directly or indirectly to the dust always present in the atmosphere and to other residues characteristic of urban and industrial environments, all of which accumulate on the lightning arrester and in particular on the radioactive source, the action of ran not being sufficient to remove it.

Owing to the poor penetration ability of the alpha particles and since the efficiency of this type of lightning arrester is based on its ionizing capacity, it is essential to eliminate all those factors which could nullify or diminish the ionizing capacity of the radioactive source.

Quantitively it may be said that the maximum penetration of the alpha particles into a medium, such as a deposit of dust on theemitting source, is only about 0.03 mm. This means that a layer of dust, or another similar deposit, of this thickness would completely nullify the effectiveness of the ionizing lightning arrester, which would then act as a conventional Franklin lightning arrester.

These disadvantages are obviated by the lightning ar-.-. rester of the invention-by means of the above-described self-cleaning device.

With the purpose of achieving the third aim emitting alpha particles and comprised of a radionuclide with a long period of half-life and which emits alpha particles of sufficiently high energy. Furthermore, the source has to be air-tight, sealed and attackproof from atmospheric agents, as well as having high specific activity. At present there are commercially available alpha emitters which meet the aforesaid conditions, constituted by radionuclides such as radium- 226 (Ra 226) and americium-24l (Am 241), which emit alpha particles with average energies of 4.8 MeV and 5.5 MeV, respectively, their half-lives being 1,620 years and 458 years, respectively.

In the lightning arrester of this invention there can be used sources of Ra-226 or Am-24l in the form of a men. 'tioned at the outset, it is necessary to provide a source metal band formed by a substrate or matrix of noble metal or alloys thereof (silver, gold, palladium etc. on to which there is applied a dispersion of an insoluble, non-volatile composition of said radio-elements, sintered in gold or other noble metal at high temperature, then proceeding with a subsequent coating by lamination and/or electroplating of a sealing lamina of noble metal or alloys thereof and lastly a layer of hard, inoxidizable metal such as nickel, with the purpose of preventing wear of the first lamina. Said laminas form a protective unit with a high degree of safety but of a suitable thickness to allow alpha particles to pass in large quantities and with high energy.

This invention is not restricted to the use of the indicated radionuclides radium-226 and americium 241, it being possible to utilize any which in the future might appear to be advantageous and suitable.

The characteristics of the radioactive source as a whole, such as has been described, are not affected by the use of a particular radionuclide. The activity, in curies, necessary to attain a given radius of protection of the lightning arrester, will be different for each radioelement, depending on the respective capacity of ionization, is. on the pairs of ions produced per curie of activity.

All the previously described characteristics will become clearer from the following description, with reference to the accompanying drawings, in which there is shown one form of embodiment given nonrestrictively by way of example and in which:

FIG. 1 is a view in perspective of a lightning arrester built in accordance with the invention;

FIG. 2 is a cross-section of a variant of embodiment; and

FIGS. 3, 4 and 5 show different forms of embodiment of the accelerating anode.

As may be seen in FIG. 1, the lightning arrester, or conductor a rod 1 which is connected to earth and which is terminated at its upper end in a point 2 which constitutes the pick-up point. The rod 1 is mounted in a support or base 3 carrying the radioactive source 4 which, in the instance described, takes the form of a band mounted above the support 3 and firmly connected thereto.

On'the rod 1 there is also mounted, by means of bearings 5, a series of arms 6 which carry at their free end vanes or cups 7, so as to constitute a mechanism of the anemometer type. From the arms 6 there extends 4, thus'removing particles of dust or dirt which may be deposited on the surface of this source, this being kept therefore clean at all times.

The bearing 5 may be of high-durability and selflubricated in order to reduce the maintenance of the unit. In addition, for maintaining the smoothness of the rotation there is provided with the bearing a cap 10 which prevents the entry of water and dust into said bearing.

In order to achieve the cleanliness of the radioactive source by means of the brush 9 with the minimum pressure of this latter, the arm 8 pivots about a spindle 11 so that when the cups and arms 6 rotate at high velocity owing to the action of the wind, the brush 9 is separated from the radioactive source by centrifugal force when the wind velocity exceeds a certain predetermined value. In this way there is prevented unnecessary wear of the radioactive source.

In accordancev with the invention, moreover, the lightning arrester is also provided with a discontinuous metal surface 12 in the form of a grid or grating, situated concentrically around the support or base 3 carrying the radioactive source 4 at a suitable distance therefrom calculated according to the maximum travel of the alpha particles in the air.

This discontinuous plate 12, which constitutes the accelerating anode, is attached to the support 3 by means of a number of arms 13 made of insulating material, for

example ceramically based, so that said plate remains insulated from the support 3 and therefore from the rod 1 connected to earth.

The support or base 3 is fixed to the rod 1 by any suitable system, for example, by means of arms 14.

The discontinuous plate 12 can have, as shown in FIG. 1, the apertures 15 of elongated, square or circular shape, as represented in FIGS. 3 and 4. This plate can also take the form of a meshwork, like that in FIG. 5.

In FIG. 2 there is shown a second variation of the invention, in which the parts or elements corresponding to the lightning arrester in FIG, 1 are designated with the same reference numerals.

In FIG. 2 the support or base 3 is frustoconically shaped where the radioactive source 4 is mounted. The shield 12 which constitutes the accelerating anode is likewise frustoconically shaped, parallel and concentric with the base 3.

These different forms of embodiment give some idea of the variations which may be introduced into the subject matter of the invention without departing from the scope thereof.

The cups 7 can adopt the shape of spherical or elliptical caps or simply plain blades. Although the actuating device of the anemometer type has always been shown mounted on the rod 1, it could also be mounted on the actual base or support of the radioactive source.

' The radioactive source may be continuous or discontinuous and mounted on the base by means of a dovetail joint or by any other system.

The foregoing description has been presented for illustrative purposes only and is not intended to limit the present invention in any way. All reasonable modifications not specifically set forth are intended to be included within the scope of the present invention, which is to be limited only by the following claims.

What is claimed is:

1. A radioactive lightning arrester apparatus, the apparatus comprising: a rod connected to the earth; a support mounted concentrically about the rod; a low energy radioactive source comprising one or more cores or nuclei disposed on said support; rotating means rotatably mounted on said rod; a plurality of arms radially emerging from said rotating means, each arm provided atits free end with a cup against which the wind acts in order to cause said rotating means to continually rotate when the wind blows; at least one link means movable with and extending from said rotating means; and a brush carried at the free end of each link, each brush situated facing the radioactive source so that said brush contacts the radioactive source to clean it as said rotating means rotates.

2. Theapparatus of claim 1 further comprising a discontinuous surface shaped in the form of a grid, said surface positioned around and spaced from said support, said surface facing at least that portion of the supsource when the wind is of a high velocity. 

1. A radioactive lightning arrester apparatus, the apparatus comprising: a rod connected to the earth; a support mounted concentrically about the rod; a low energy radioactive source comprising one or more cores or nuclei disposed on said support; rotating means rotatably mounted on said rod; a plurality of arms radially emerging from said rotating means, each arm provided at its free end with a cup against which the wind acts in order to cause said rotating means to continually rotate when the wind blows; at least one link means movable with and extending from said rotating means; and a brush carried at the free end of each link, each brush situated facing the radioactive source so that said brush contacts the radioactive source to clean it as said rotating means rotates.
 2. The apparatus of claim 1 further comprising a discontinuous surface shaped in the form of a grid, said surface positioned around and spaced from said support, said surface facing at least that portion of the support occupied by the radioactive surface.
 3. The apparatus of claim 1 wherein said support and said radioactive source are circular.
 4. The apparatus of claim 1 wherein said radioactive source emits low energy alpha particles.
 5. The apparatus of claim 1 and further comprising means for disengaging said brush from said radioactive source when the wind is of a high velocity. 